1. Season chicken with 1/4 teaspoon salt and with pepper. In a large frying pan with a lid, heat 2 tablespoons of olive oil and cook chicken in batches over medium-high heat, turning once or twice, until browned, about 6 minutes per batch. Add sausage and cook until browned, about 5 minutes. Remove chicken and sausage from pan with a slotted spoon.
2. Add remaining 1 tablespoon oil to pan along with onion and bell pepper, reduce heat to medium, and cook, stirring often, until softened, about 5 minutes. Add rice, remaining 3/4teaspoon salt, hot pepper, and saffron. Cook 1 minute, stirring to coat rice with oil. Add broth and wine and return chicken and sausage to pan. Cover, reduce heat to medium-low, and simmer 12 minutes.
3. Add tomatoes, shrimp, and clams, pushing shellfish into rice. Simmer, covered, until rice is tender, chicken juices run clear when pricked, and clams have opened, 10 to 15 minutes longer. Discard any clams that do not open. Stir to combine ingredients. Serve at once, with scallions sprinkled on top.